The present invention relates in general to an electromagnetic induction heating apparatus and, in more particular, to an electromagnetic induction heating apparatus which generates a high-frequency alternating field for the induction heating of a cooking pot or kettle serving as a load for household use, thereby cooking food contained in the kettle.
In electromagnetic induction cookers, a high frequency current is supplied from an inverter circuit to a heating coil, which generates a high-frequency magnetic field for subjecting a metallic cooking kettle, along with the food contained therein, to induction heating. For effective induction heating of the kettle, the impedance of the metallic kettle serving as the load should preferably be of a given value or more, since, if the impedance is low, the current flowing through the heating coil will increase, resulting in an increase in coil loss. In view of such factors, currently available materials for the cooking kettle are limited to ferromagnetic materials (preferably iron), and the heaters are so designed that induction heating is automatically stopped when a vessel made of a nonmagnetic material, such as aluminum, is used. Thus, in heating food by using one such prior art electromagnetic induction cooker, a cooking kettle needs to be made of iron. If a cooking kettle made of another nonmagnetic material, such as aluminum, is used for this purpose, effective induction heating cannot be achieved and the cooking process requires greater time and power consumption. In fact, vessels made of aluminum or other nonferrous metals (nonmagnetic materials), such as aluminum kettles aluminum pots, etc., are being increasingly used in households, since they have certain advantages. Thus, not being abreast of the varied vessels in current use, conventional electromagnetic induction cookers cannot make the most of their inherent merits as cooking machines.